In conventional magnetic disc apparatus, information is recorded in concentric tracks. The line recording density is low in the tracks located on or near the periphery of the recording media because data is recorded on all tracks at an identical recording frequency with the recording media turning at the fixed speed. In tracks located on or near the periphery this results in an increase in the minimum interval of recording media occupied by a unit of information. Therefore, the recording capacity per unit area of media is lower and the efficiency of the recording density is lower along these outer tracks.
Recently, attempts have been made to improve recording density by using a Zone Bit Recording (ZBR) system to equalize the line density in each track. In such a system, tracks in the media are organized in a plurality of zones and the line recording density in all zones is made uniform. The line recording density in the tracks at the periphery is thus the same as in the interior tracks. This is achieved by recording the data in a particular zone using a frequency which will cause the line recording density to be the same as in tracks in other zones. However, a ZBR system has several disadvantages.
Typically, information is read from the disc using a peak detection/differentiation scheme. However, shifts in the position of the peaks often occur due to interference from adjacent peaks and low signal to noise ratios. A regeneration circuit is typically used to counteract such interference.
In a ZBR system, the bandwidth of the frequency of the signal to be regenerated differs in each zone corresponding to the difference in the recording frequency used to record the data in the particular zone. It is necessary to optimize the regeneration by changing the characteristics of the regenerating circuit for each zone in order to maintain the reliability of the data. A conventional approach is to provide a separate regeneration circuit for each zone. However, the limited space in a typical compact magnetic disc apparatus does not permit an substantial increase in the number of circuit elements.